Arrangement for cooling the piston of internal combustion engines



y 1957 SCHMIDL 2,800,119

ARRANGEMENT coouue THE PISTON OF INTERNAL COMBUSTION mamas Filed May 5,1955 INVENTOR United States Pate ARRANGEMENT :FoR cooLlNG THE PISTON- orINTERNAL COMBUSTION ENGINES I Rudolfl-SchmidL Numberg, Germany,assignonto Maschinenfabrik Augsburg-Numberg. A; G., Numberg, Germany:

Application-May 5, 1955, Serial No. 506,329

z-Claims.v (Cl. 12341.35)

Thisinventionrelatee-to anarrangement for-cooling thepisto'n ofinternal. combustion engines; andmore parpiston head, by means of athrowing device, preferablyar nozzle, under action of the full pressureof the oil in the lubricating system.

In high-duty diesel engines tor trucksa jet of oil is continuouslysprayed against the piston .headin order to .con-

trol the temperature of the piston, and 'especia'lly'of the piston head.Normallythe oililis:sprayed into each of the cylinders through a nozzlewhichds supplied .with oil from the main oiling circuit. The nozzletends-to become obstructed by impurities of the oil. In order to avoidthis, the diameter of the nozzle had to be made larger than re quiredfor the proper purpose of the nozzle. Thus, for instance, it has beenfound by practical experiences that the diameter of the nozzle shouldnot be less than 1.5 mms. With such a nozzle diameter, however, theamount of fuel flowing oil through all of the nozzles of a multicylinderengine is very considerable. For instance, with an 8-cylinder engine incase of the above mentioned nozzle diameter of 1.5 mms., the totalnozzle cross section for all cylinders would be about 14 mm. Referringthis to a single symbolic substitute nozzle this would correspond to anozzle diameter of about 3.5 mms. However, it has been found bypractical measurements that the entire lubricating oil throughput of theengine is adapted only to the cross section of a symbolic substitutenozzle of about 4.5 mms. diameter, which shows that the share oflubricating oil flowing out through the spray nozzle is a veryconsiderable one. Hence a sufiicien-tly large lubricating oil pressuremust be accumulated in order that all oil consuming points of the engineare supplied with a sufficient amount of oil. This again requires asufficiently high delivery of the oil circulation pump. Such large oilcirculation pumps, however, are disadvantageous with a view to theefiiciency of the engine, since they absorb a considerable amount ofenergy which must be supplied by the engine. On the other hand, if theoil circulation pump is too small in relation to the oil sprayingnozzles for cooling the piston, the lubricating oil pressure with slowor idle run of the engine will break down nearly to zero because theamount of oil which is supplied is decreasing proportional to the speedof the engine while the cross section of the nozzles remains unchanged.

Hereat the drawback exists that during slow or idle run of the enginethe lubricating oil, following the path of lowest resistance, isdischarged mainly from the nozzles having a relatively large bore whilefor instance the bearings will be supplied with a very small portion ofthe lubricating oil only, and that at a point of time where there is noactual necessity for cooling the piston or the piston head,respectively.

ice

Itwill he -understood that similar conditions may occur where inplaceofnozzles any other device is used for sprayingthemil against: thepistonhead and where for constructional reasons the throughput of oilfor cooling the piston must be made larger than normally required.

It is an object of the presentinvention to provide means for'avoidingthese drawbacks.-

More particularly, it is anobject of theinvention to control the shareof lubricating oil branched 01$ for. cooling-thepistonor.thehead of. thepiston, in dependence upon the'speed of the engine.

With these and further objects in view, accordingto the.presentinventiomthedevice-for branching off cooling oil from the-mainoiling circuit and-casting it against the pistonihead .is provided withacheck valve which iscontrolledoby the oil pressure of the main oilingcircuit, independently of the relief pressure valve normally arranged inthe. oilingcircuit, in such. away that in case of a decrease of..thispressure to .aspredetermined lower limit, e. .g.-,.the idle run pressureof the oil pump, the discharge of-oilfrom the spraying device is.automatically prevented. Where" a'nozzleis used as .an injecting device,in per se knownmanner, a non-return valve is arranged inthe duct,to=,the nozzle, said non-return valve responding to the pressureprevailing in themai-noiling circuit at slow or idle run .ofthe engine,in such away that the oil in this conditiomofipperation is preventedfrom issuing from the In-this manneritis: possible totdesign-the oilpump for a much smaller output without in any way reducing the elfectivecooling capacity at the piston.

Other and further objects, features and advantages of the invention willbe pointed out hereinafter and appear in the appended claims formingpart of the application.

In the accompanying drawings a now preferred embodiment of the inventionis shown by way of illustration and not by way of limitation.

Fig. l is an axial section through an injection type internal combustionengine with a nozzle for the piston cooling jet connected to the mainoiling circuit, the nozzle with nozzle holder being partly shown in aperspective view;

'Fig. 2 is a side view, partly in section, showing the nozzle and thenozzle holder on a larger scale.

Similar reference numerals denote similar parts in the two figures.

Referring now to the drawing, and first to Fig. 1, it will be seen thatthe engine is a conventional injection-type internal combustion enginein which the combustion chamber 11 is provided in the head of the piston1 jointed to a piston rod 15 and reciprocating in a cylinder 12 having acover 13 in which the fuel nozzle system 14 is accommodated. Provided inthe crank case is a nozzle holder 6 supporting a nozzle 3 through whichlubricating oil is sprayed against the inner wall of the piston head 2.

The oil is delivered from a sump 16 through oil pump 17 into a mainoiling circuit 19 from which parallelly connected lines 4 and 20 lead,respectively, to a cooling oil branch circuit and lubricating oil branchbranch circuit for the lubrication points of the engine. The oil isreturned to sump 16 either by drainage from the crankcase and/or throughreturn 21. In case of an excess of pressure at the relief-pressure valve18, the same will permit a portion of the oil to return directly to thesump 16, through a pipe 22, for keeping the pressure in the main oilingcircuit within the normal limits.

As shown in Fig. 2 in greater detail, branch cooling oil circuit 4contains the nozzle holder 6 accommodating a non-return valve 7 which isacted upon by a compression spring 8. The lubricating oil is fed fromthe branch cooling oil duct 4 connected to main oiling circuit pipe 19,

through a non-return valve 7 and the channelS in the nozzle holder 6, asindicated by the arrows 9. A cleaning opening 10 at the left hand end ofthe nozzle holder is normally closed by a plug 23. The tension of thespring 8 is adapted insuch a way that the same normally is overcome bythe pressure prevailing in 'the oil duct 4, so that the valve 7 innormal operation of the engine remains always open, for spraying oilthrough the nozzle 3 against the piston head 2. Only when the oilpressure falls below a predetermined value which has been adjusted bythe tension of the spring 8, the Valve 7 will be closed by the springpressure which now preponderates, whereby the supply of oil to thenozzle 3 is checked and lubricating oil can flow only totheremaining-lubricating points, and more particularly to the bearingsof'the engine. 7

The valve 7 before the spray nozzle 3 has nothing' to do With the'reliefpressure valve 18 arranged in the lubricating oil circuit and serving toreturn a surplus of lubrieating oil to the sump 16, and it is quiteindependent of said relief pressure valve as to its function.

It will be appreciated that the oil pressure will fall below the abovementioned critical value for instance during slow or idle run of theengine. In this case, however, the amount of heat transmitted to thepiston is relatively small, so that it is not necessary for the pistonhead to be sprayed with cooling oil in this Working condition.

While the invention has been described in detail with respect to a nowpreferred example and embodiment'of the invention it will be understoodby those skilled in the art after understanding the invention thatvarious changes and modifications may be made without departing from thespirit and scope of the invention and it is intended,

therefore, to cover all such changes and modifications in the appendedclaims.

I claim:

1. In an internal combustion engine such as a high output Diesel enginehaving a main oiling circuit, an oil circulating pump in said maincircuit, at least one lubrication branch circuit leading from said maincircuit to the engine lubrication points, and at least one pistoncooling branch circuit leading from the main circuit to a spray nozzlefor spraying cooling oil into the hollow interior of a piston, bothbranch circuits being connected in parallel to said main oiling circuit,respectively, the improvement comprising a spray nozzle in said pistoncooling branch circuit having an opening of a size to provide a flowresistance to the passage of oil less than the flow resistance in thelubricating branch circuit at engine idling speeds, a check valveconnected to said nozzle, and means for opening said valve under thepressure of the main oiling circuit during normal engine running speeds,but for closing said valve during low running or engine idling speeds. V

2. In an internal combustion engine as in claim 1, said opening andclosing means comprising a spring automatically responsive to the oilpressure in said main oiling circuit.

References Cited in the file of this patent UNITED STATES PATENTS1,992,339 Winslow Feb. 26, 1935 FOREIGN PATENTS 833,880 Germany Mar. 13,1952 1037,0224 France Apr. 29, 1953

